Heavy rain from thunderstorms which developed over the Scratch Gravel Hills burn scar caused a debris flow which damaged a home and washed out railroad tracks.
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The episode as NWS TFX wrote it up.
Heavy rain from thunderstorms which developed over the Scratch Gravel Hills burn scar caused a debris flow which damaged a home and washed out railroad tracks.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Great Falls, MT wrote its last area forecast discussion before the first event at Jul 20, 1:53 PM MST, 7 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREAT FALLS MT 253 PM MDT FRI JUL 20 2012 .DISCUSSION... TONIGHT THROUGH SUNDAY...FORECAST CONTINUES TO LOOK ON TRACK FOR THE UPPER LEVEL WAVE TO MOVE THROUGH NORTHWEST MONTANA THIS AFTERNOON AND EVENING. NUMEROUS THUNDERSTORMS ARE IN PROGRESS OVER THE IDAHO PANHANDLE WITH SCATTERED THUNDERSTORMS BEGINNING TO DEVELOP OVER MY SOUTHWEST AND WEST CENTRAL ZONES. ACTIVITY ACROSS THE WESTERN HALF OF MY CWA WILL INCREASE THROUGH THE AFTERNOON AND EVENING HOURS. STILL APPEARS TO BE A RISK FOR A FEW STORMS TO BECOME STRONG TO SEVERE...MAINLY OVER MY NORTHWEST ZONES. HOWEVER...AT LEAST ONE MODEL DEVELOPS A SECOND BAND OF POTENTIALLY SEVERE THUNDERSTORMS FROM THE LITTLE BELT MOUNTAINS TO NORTHERN FERGUS AND SOUTHERN BLAINE COUNTIES DURING THE EVENING HOURS. EVEN FOR STORMS THAT ARE EXPECTED TO REMAIN SUB-SEVERE THERE IS A DISTINCT RISK FOR VERY HEAVY AND INTENSE RAIN IN A SHORT PERIOD OF TIME CAUSING LOCALIZED FLOODING. ACTIVITY SHOULD MOVE INTO NORTHEAST MONTANA AFTER MIDNIGHT WITH SKIES CLEARING FROM THE SOUTHWEST. SATURDAY SHOULD BE ANOTHER WARM AND GENERALLY DRY DAY WITH PERHAPS A RISK OF AN ISOLATED STORM OR TWO OVER THE SOUTHWEST MONTANA MOUNTAINS DURING THE AFTERNOON AND EVENING. TEMPERATURES WARM UP A FEW MORE DEGREES ON SUNDAY WITH MONSOON MOISTURE INCREASING FROM SOUTH TO NORTH THROUGH THE DAY. MODELS ARE BEGINNING TO COME INTO BETTER AGREEMENT THAT SCATTERED THUNDERSTORMS WILL DEVELOP OVER SOUTHWEST AND SOUTH CENTRAL MONTANA...POSSIBLY AS FAR NORTH AS A LINE FROM HELENA TO GREAT FALLS TO LEWISTOWN. THE ALSO APPEARS TO BE AT LEAST A SLIGHT RISK FOR SOME STORMS TO BECOME STRONG TO SEVERE. MPJ SUNDAY NIGHT THROUGH FRIDAY...LONG-RANGE FORECAST MODELS MAINTAINING GOOD CONSISTENCY AND AGREEMENT ON EXPECTED CONDITIONS FOR THE WEEK AHEAD. PERIOD BEGINS WITH BROAD UPPER LEVEL RIDGE DRIFTING INTO ERN MT ON SUN EVE...ALLOWING MONSOONAL MOISTURE TO GENERATE SCATTERED SHOWERS AND THUNDERSTORMS SUN NIGHT MAINLY OVER SOUTHWEST MT. SOUTHWEST FLOW ALOFT OVER OUR REGION STRENGTHENS ON MONDAY IN RESPONSE TO A VIGOROUS PACIFIC LOW PRESSURE SYSTEM MAKING ITS WAY ALONG THE US/CAN BORDER. A SURFACE COLD FRONT FROM THIS SYSTEM SHOULD CROSS THE CONTINENTAL DIVIDE MONDAY EVE WHERE IT WILL TAP INTO THE MONSOONAL MOISTURE TO BRING ANOTHER ROUND OF THUNDERSTORMS...WITH MODELS SHOWING WIDER COVERAGE OF STORMS PARTICULARLY OVER THE CENTRAL MT COUNTIES. MODELS HAVE ALSO SLIGHTLY INCREASED PRECIPITABLE WATER VALUES...THOUGH SURFACE DEW POINTS ARE SOMEWHAT DRY...SO A MIX OF DRY/WET STORMS SEEMS LIKELY. THE COLD FRONT WILL BE WELL DOWNSTREAM BY TUES MORNING AS THE LOW PRESSURE CENTER LIFTS INTO SRN ALBERTA. WESTERLY FLOW AND A RETURN TO DRY CONDITIONS DEVELOP BEHIND THE FRONT ALONG WITH SOME BREEZY TO LOCALLY GUSTY WINDS ON TUES...LIKELY INCREASING WILDLAND FIRE DANGER OVER PORTIONS OF CENTRAL/SOUTHWEST MT. THE UPPER LEVEL RIDGE GRADUALLY REBUILDS OVER THE NRN ROCKIES THRU MIDWEEK AND THE NEXT PUSH OF MONSOONAL MOISTURE BEGINS TO ARRIVE THURS WITH SCATTERED THUNDERSTORMS POSSIBLE THURS AND FRI EVENING. HIGH TEMPERATURES REMAIN ABOUT 5-8 DEGREES ABOVE NORMAL ON MON BUT THE COLD FRONT PASSAGE WILL DROP BACK HIGHS INTO THE LOW-MID 80S FOR TUES/WED. TEMPS THEN REBOUND UPWARD A FEW DEGREES EACH DAY FOR THE LATTER HALF OF THE WEEK...REACHING THE UPPER 80S TO LOW 90S BY FRIDAY. WARANAUSKAS && .AVIATION... UPDATED 1740Z. VFR CONDITIONS EXPECTED TODAY WITH WIDESPREAD MID-LEVEL CEILINGS OVER CENTRAL/SOUTHWEST MT. UPPER LEVEL TROF CURRENTLY IN NORTHERN OREGON WILL MOVE TO NORTHWEST MT BY THIS EVE. INCREASING INSTABILITY AND VEERING WINDS FROM THE APPROACHING TROF WILL LEAD TO DEVELOPMENT OF SCATTERED STRONG-TO-SEVERE THUNDERSTORMS THIS AFTN/EVE... ESPECIALLY ALONG LINE FROM KCTB TO KHVR. STORM ACTIVITY WILL ALSO EXTEND SOUTH TO KGTF/KHLN/KLWT BUT HAVE LESSER CHANCE OF SEVERE CONDITIONS THERE. BRIEF MVFR CONDITIONS FROM HEAVY RAINFALL AND STRONG SHIFTING OUTFLOW WINDS POSSIBLE NEAR ANY STORM CELLS. SKY COVER WILL DIMINISH OVER AERODROMES AFTER 06Z. BRITTON && .PRELIMINARY POINT TEMPS/POPS... GTF 59 89 57 92 / 30 0 10 10 CTB 54 82 50 89 / 40 0 10 10 HLN 58 90 58 93 / 30 10 10 20 BZN 51 92 50 93 / 10 10 10 20 WEY 42 81 41 83 / 20 10 10 20 DLN 52 88 52 89 / 10 10 10 20 HVR 60 90 55 93 / 30 10 10 10 LWT 56 87 54 89 / 30 10 10 10 && .TFX WATCHES/WARNINGS/ADVISORIES... NONE. && WEATHER.GOV/GREATFALLS
HAZARDOUS WEATHER OUTLOOK...UPDATED NATIONAL WEATHER SERVICE GREAT FALLS MT 1040 AM MDT FRI JUL 20 2012 MTZ009>013-044>051-211200- NORTHERN ROCKY MOUNTAIN FRONT-EASTERN GLACIER-HILL-CASCADE- CHOUTEAU-TOOLE-LIBERTY-EASTERN PONDERA-BLAINE- SOUTHERN ROCKY MOUNTAIN FRONT-EASTERN TETON-JUDITH BASIN-FERGUS- 1040 AM MDT FRI JUL 20 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL MONTANA AND NORTH CENTRAL MONTANA. .DAY ONE...TODAY AND TONIGHT SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED ACROSS NORTH CENTRAL MONTANA TODAY. SOME STORMS COULD BE SEVERE...WITH DAMAGING WINDS...LARGE HAIL...FREQUENT LIGHTNING...AND HEAVY RAINFALL. VERY HEAVY RAIN IN SHORT AND INTENSE BURSTS COULD LEAD TO LOCALIZED FLOODING. THE BEST TIME FRAME FOR SEVERE WEATHER TO OCCUR WILL BE FROM NOON UNTIL 9 PM TODAY. BE PREPARED FOR POSSIBLE SEVERE THUNDERSTORMS THIS AFTERNOON AND EVENING. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION MAY BE NEEDED THIS AFTERNOON AND EVENING. ANY SPOTTER REPORTS OF SEVERE WEATHER WOULD GREATLY BE APPRECIATED. MTZ008-014-015-052>055-211200- BEAVERHEAD-CENTRAL AND SOUTHERN LEWIS AND CLARK-MADISON-JEFFERSON- BROADWATER-MEAGHER-GALLATIN- 1040 AM MDT FRI JUL 20 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHWEST MONTANA. .DAY ONE...TODAY AND TONIGHT THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.
The national radar mosaic for the moment the first event began.
1 debris flow, 1 flash flood. Local standard time, as filed.
Flash flooding in burn area of the Scratch Gravel Hills. Water over some roads and ash three inches deep flowing into a home.
Railroad tracks washed out near Scratch Gravel Hills.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2012Every state in 2012This day in weather historyWarnings in Montana, July 2012
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 405131, 405132.